MAX7219 Serial 8 digit seven segment display driver

[Jhonny]

http://www.ccsinfo.com/forum/viewtopic.php?t=38882
I would like to ask for help. I use your code and very good. Thank you for sharing! The problem is that the removal of the power (and then back switch) can not initialize the MAX7219. Only "8" show numbers. When very quick to turn off and on the power supply, is there a way to pop in a good display and it works fine. The MAX7219 is connected correctly and the 10uF +100 nF is soldered onto the power supply terminals. I tried to increase the delays - without success ... A PIC18F2620 is driven at 20MHz. What could be the problem? I've changed my MAX7219, but it may not solved the problem. Please help me! (I'm going crazy)

[arunb]

I think its an issue with power up timings. Maybe you should reset the 7219's supply from the PIC after startup.

Does the 7219 communicate in this condition ??

thanks
a

[Jhonny]

Yes, it works ... but only sometimes. May require that the normal departure, when the power source off and on very quickly. It's no good if the power goes out because the display does not start correctly. I tried a delay to the start of the program, the MAX7219 to first "wake up" and then initialize the program. Unfortunately, the result has been even worse.

[Ttelmah]

Try clearing the display test register.

It sounds as if the 7219, is seeing a spike on a select/clock, and going into an unexpected mode. If the display_test register bottom bit gets set, it'll sit with all segments on ('8' displayed), and won't accept any other commands till this bit is cleared. Since it is register 0xF, a clock signal seen with everything else high, could give this behaviour.

Best Wishes

[Jhonny]

Ttelmah!
Bull's-eye! That was the problem! But it is in the program, but has been commented out, I do not know why?
Thank you very much for your help!

[Ttelmah]

Glad I hit it.